Secure Delete accompanied by a noise?

I was secure deleting a ton of crap the other day (like over 1000 files) and my computer made the faintest like hissing noise. I couldn't figure out wth it was until i heard the trash can delete noise.
must have been the secure delete working hard.

A secure delete writes over the old files you're tossing away with garbage characters, so the act of the secure delete is very hard-drive access intensive. The sound you're hearing is probably the arm on the drive accessing platters. If you hear klunking, that means the arm isn't accessing properly and your hard drive is about to poo the bed.

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